work was the dense fog which, it has
been already mentioned, at that time enveloped not only that part of
Europe, but almost the entire world.

Never failing to turn to the best advantage the few intervals when the
mist lifted a little, the astronomer would at the same time cast an
inquiring glance at the firmament, as he was greatly interested in the
revision of the chart of the heavens, in the region contiguous to the
constellation Gemini.

To the naked eye this constellation consists of only six stars, but
through a telescope ten inches in diameter, as many as six thousand
are visible. Rosette, however, did not possess a reflector of this
magnitude, and was obliged to content himself with the good but
comparatively small instrument he had.

On one of these occasions, whilst carefully gauging the recesses of
Gemini, he espied a bright speck which was unregistered in the chart,
and which at first he took for a small star that had escaped being
entered in the catalogue. But the observation of a few separate nights
soon made it manifest that the star was rapidly changing its position
with regard to the adjacent stars, and the astronomer's heart began to
leap at the thought that the renown of the discovery of a new planet
would be associated with his name.

Redoubling his attention, he soon satisfied himself that what he saw was
not a planet; the rapidity of its displacement rather forced him to
the conjecture that it must be a comet, and this opinion was soon
strengthened by the appearance of a coma, and subsequently confirmed, as
the body approached the sun, by the development of a tail.

A comet! The discovery was fatal to all further progress in the
triangulation. However conscientiously the assistant on the Spanish
coast might look to the kindling of the beacon, Rosette had no glances
to spare for that direction; he had no eyes except for the one object of
his notice, no thoughts apart from that one quarter of the firmament.

A comet! No time must be lost in calculating its elements.

Now, in order to calculate the elements of a comet, it is always deemed
the safest mode of procedure to assume the orbit to be a parabola.
Ordinarily, comets are conspicuous at their perihelia, as being their
shortest distances from the sun, which is the focus of their orbit,
and inasmuch as a parabola is but an ellipse with its axis indefinitely
produced, for some short portion of its pathway the orbit may be
indifferently cons